FR3099804A1 - Aircraft reverser comprising a braking mechanism for a movable cowl in the event of overtravel - Google Patents

Abstract

The invention relates to a thrust reverser for an aircraft propulsion unit, of the type having a cowl movable between a closed position allowing the propulsion unit to generate thrust and an open position allowing the propulsion unit to generate a braking back thrust of the aircraft. According to the invention, the reverser comprises braking elements (24, 25) such as a groove (24) and a pin (25) respectively secured to a fixed part (26) of the reverser and of the movable cowl. . These braking elements (24, 25) are configured to cooperate with each other by sliding with friction when the movable cover performs an overtravel (C2), beyond the open position, so as to generate a braking force opposing this movement. In a preferred embodiment, the groove (24) comprises for this purpose a section restriction (E1) along the direction (D2) of movement of the movable cowl. Figure for the abstract: Fig. 8

Description

Aircraft reverser comprising a mechanism for braking a movable cowl in the event of overtravel

The invention relates to the field of thrust reversers for aircraft propulsion systems. The invention relates more specifically to the axial retaining mechanism of the mobile external structure of such an inverter.

State of the prior art

Generally speaking, a thrust reverser can be placed in a direct jet configuration, allowing the propulsion assembly to generate thrust, and in a reverse jet – or reverse thrust – configuration in which some of the gases circulating in the propulsion assembly is redirected towards the front of the propulsion assembly, thus generating a braking counter-thrust of the aircraft.

To do this, inverters generally include a movable external structure such as a sliding cowl. In direct jet, the cowl is in a closed position so as to guide a flow of fluid in the propulsion assembly, this flow contributing fully to the thrust. In reverse jet, the cowl is in an open position so as to release a radial opening configured to evacuate part of the fluid flow from the propulsion assembly, in order to generate counterthrust.

In a conventional reverser, for example that described in document WO 2011/064479 A1, actuators such as cylinders are provided to open and close the cover. During its movement between the closed and open positions, the cowl is guided by rails or slideways fixed to a fixed part of the propulsion assembly.

In the event of breakage or absence of such a cowl control actuator, the aerodynamic forces applied to the cowl in the flight phase are likely to move it beyond the open position and cause it to disengage relative to the rails or guide rails.

To prevent too great a recoil of the cover and therefore its disengagement during operation of the reverser, it is known from document WO 2015/040347 A1 to arrange an axial stop at least on one of the rails or guide rails.

Such a stop requires at least locally oversizing the structure to which it is attached given the kinetic energy of the cowl during its collision with the stop, which tends to increase the mass of the reverser as well as its cost.

The invention aims to provide a thrust reverser capable of retaining the mobile external structure in the event of failure or absence of a control actuator for this structure, while avoiding the drawbacks associated with a conventional axial thrust bearing.

To this end, the subject of the invention is a thrust reverser for an aircraft propulsion assembly, this reverser comprising a fixed structure and a mobile external structure, this reverser being configured to be placed in:
– a direct jet configuration in which the mobile external structure is in a closed position, the mobile external structure in the closed position being capable of guiding a flow of fluid in the propulsion assembly so as to generate thrust,
– an inverted jet configuration in which the mobile external structure is in an open position, the mobile external structure in the open position giving off a radial opening capable of evacuating part of said fluid flow from the propulsion assembly so as to generate counter thrust.

Moving the mobile external structure from the closed position to the open position defines a positive direction of movement.

The invention is characterized in that the fixed structure comprises a first braking element and the mobile external structure comprises a second braking element, the first and the second braking element cooperating with each other by sliding with friction when the mobile external structure is moved in the positive direction beyond the open position so as to generate a braking force opposing this movement, the first and the second braking element being configured so that the force braking increases when the mobile external structure moves away from the open position.

Such an inverter makes it possible to avoid a sudden collision between the mobile external structure and the fixed structure by damping the mobile external structure when the latter performs an overtravel, by being moved in the positive direction beyond the opening position under the action of aerodynamic forces, in particular in the event of rupture of a control actuator of the mobile external structure during operation of the reverser in the flight phase.

Such damping of the mobile external structure makes it possible to reduce the mass and the cost of the reverse gear compared to a reverse gear in which the axial retention is ensured by a conventional thrust bearing.

The invention also makes it possible to simplify the assembly of the reverser since the axial retention of the mobile external structure does not require equipping the reverser with an axial stop.

In addition, the braking elements can be configured in such a way as to define continuous force paths ensuring a smooth transition between the travel of the mobile external structure upstream of the open position and its overtravel downstream of this position.

More generally, the invention makes it possible to improve the absorption of the kinetic energy of the movable external structure when its travel is interrupted beyond the open position and to preserve the structural integrity of the reverser while avoiding oversizing of the elements ensuring the axial retention of the mobile external structure.

Preferably, the first and the second braking element can be configured so that the braking force comprises at least one component perpendicular to a direction of movement of the mobile external structure.

The direction of movement of the movable external structure corresponds to a direction along which the movable external structure moves when the reverser changes from the direct jet configuration to the reverse jet configuration.

In one embodiment, one of the first and the second braking element can comprise at least one guide element such as a slider and the other of the first and the second braking element can comprise at least one guided such as a pin, said braking force resulting from the cooperation between the guide element and the guided element.

Thus, for example, according to a first alternative, the first braking element belonging to the fixed structure can comprise one or more slideways and the second braking element belonging to the mobile external structure can comprise one or more pins cooperating with the slider(s) of so as to produce the braking force. According to a second non-limiting alternative, the first braking element belonging to the fixed structure can comprise one or more studs and the second braking element belonging to the mobile external structure can comprise one or more slides cooperating with the stud(s) so as to produce the braking force.

Preferably, the guide element(s) (eg slideways) of the first braking element (first alternative) or of the second braking element (second alternative) can be substantially parallel to the direction of movement of the mobile external structure.

The first braking element (first alternative) or the second braking element (second alternative) can for example comprise two guide elements (eg slideways) substantially parallel to each other.

In one embodiment, the at least one guide element can form a groove configured to receive the at least one guided element, this groove having a dimension which varies according to the direction of movement of the mobile external structure.

Such a variation in dimension makes it possible to modify the frictional force between the first and the second braking element according to the relative position of the first and the second braking element with respect to each other along the direction of displacement of the mobile external structure, in particular making it possible to increase the braking force when the mobile external structure moves away from the closed position.

The inverter may comprise first guide means configured to guide the mobile external structure between the closed position and the open position and second guide means configured to guide the mobile external structure when the latter is moved in the direction positive from the open position, these second guide means comprising the first and second braking elements.

In one embodiment, the reverser may comprise a slider secured to one of the fixed structure and the mobile external structure and a sliding element secured to the other of the fixed structure and the mobile external structure, this slider forming a a first groove configured to receive said sliding element, the slider forming a second groove forming one of the first and the second braking element, the second groove being configured to receive the other of the first and the second braking element.

Said sliding element may preferably form one of said first guide means and said first groove may form another of said first guide means.

In one embodiment, the braking element received by said second groove can be integral with and/or be carried by said sliding element.

The reverser may comprise a stopper configured to prevent movement of the mobile external structure in said positive direction beyond a stop position, the stopper being configured so that the mobile external structure is subjected to said braking force when it is moved in the positive direction between the open position and the stop position.

When the reverser comprises such a stop, one of the first and the second braking element can be configured to cooperate with the stop when the mobile external structure is moved to the stop position so as to immobilize the structure mobile external in the stop position.

In one embodiment, one of the stopper and the braking element cooperating with this stopper can be configured to be plastically deformed by the other of the stopper and the braking element cooperating with this stopper when the external structure mobile is moved to the stop position.

Such plastic deformation makes it possible to prevent the mobile external structure from returning to the closed position.

The invention also relates to an aircraft propulsion assembly, this propulsion assembly comprising a thrust reverser as defined above, as well as an aircraft comprising such a propulsion assembly.

Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows.

The following detailed description refers to the attached drawings in which:

is a diagrammatic view in axial section of an aircraft propulsion assembly in accordance with the invention, this propulsion assembly comprising a twin-spool turbofan engine;

is a schematic half-view in axial section of a thrust reverser according to the invention, in a direct jet configuration;

is a schematic half-view in axial section of the reverser of FIG. 2, in an inverted jet configuration;

is a schematic perspective view of part of a thrust reverser according to the invention, showing a mechanism for guiding the movable external structure of this reverser;

is an enlargement of part of Figure 4, centered on said guide mechanism;

is a schematic perspective view of a propulsion assembly of the prior art, this propulsion assembly comprising a thrust reverser whose movable external structure is shown in a tilting position;

is a schematic cross-sectional view of a guiding and braking mechanism of a mobile external structure of a thrust reverser according to the invention, in a configuration in which the mobile external structure is between a closed position and an open position, this mechanism comprising a pin secured to the mobile external structure received in a groove of a fixed structure of the reverser;

is a diagrammatic view in longitudinal section of the mechanism of FIG. 7, showing the pin in a position in which it does not interact with the groove, this position corresponding to a position of the movable external structure between the closed and closed positions 'opening ;

is a diagrammatic view in longitudinal section of the mechanism of FIG. 7, showing the pin in a position corresponding to the open position of the mobile external structure;

is a diagrammatic view in longitudinal section of the mechanism of FIG. 7, showing the pin in a stop position corresponding to a position of the mobile external structure located beyond the open position;

is a diagrammatic view in longitudinal section of the mechanism of FIG. 7, showing the pin in a stop position in which it is retained by an abutment after having been plastically deformed by this abutment.

Detailed description of embodiments

There is shown in Figure 1 an aircraft propulsion unit 1 comprising a turbomachine 2 shrouded by a nacelle 3. In this example, the turbomachine 2 is a twin-spool turbofan engine.

Subsequently, the terms “upstream”, “downstream”, “front” and “rear” are defined with respect to a direction D1 of gas flow through the propulsion assembly 1 when the latter is propelled.

Conventionally, the term "direction" designates a line, generally straight, along which a fluid or an object can for example be moved, and the term "direction" designates an orientation of such a movement, in particular according to a direction.

The turbojet engine 2 has a longitudinal central axis A1 around which its various components extend, in this case, from upstream to downstream of the turbojet engine 2, a fan 4, a low pressure compressor 5, a high pressure compressor 6 , a combustion chamber 7, a high pressure turbine 8 and a low pressure turbine 9. The compressors 5 and 6, the combustion chamber 7 and the turbines 8 and 9 form a gas generator.

Conventionally, during the operation of such a turbojet engine 2, an air flow 10 enters the propulsion assembly 1 through an air inlet upstream of the nacelle 3, crosses the fan 4 and then divides into a flow central 10A primary and a 10B secondary stream. The primary stream 10A flows in a primary gas circulation stream 11A passing through the gas generator. The secondary flow 10B flows for its part in a secondary stream 11B surrounding the gas generator and delimited radially towards the outside by the nacelle 3.

The invention relates to a thrust reverser 12 as shown in Figures 2 and 3, or in Figure 4, to reverse the thrust generated by such a propulsion unit 1.

With reference to FIGS. 2 and 3, the reverser 12 comprises on the one hand elements fixed with respect to a stator of the turbojet engine 2, among which a fixed internal structure 13, a front frame 14 and grids 15 carried by the front frame 14.

This reverser 12 further comprises movable elements with respect to the aforementioned fixed elements, among which a movable external structure 16 forming in this example a sliding movable cowl, shutters 17 and connecting rods 18. These movable elements make it possible to modify the configuration of the inverter 12.

Figure 2 shows Inverter 12 in a direct jet configuration. In this configuration, the movable cowl 16 is in a closed position in which it bears axially against the front frame 14 covering the grilles 15.

In direct jet, the movable cowl 16 and the fixed internal structure 13 radially delimit between them a downstream part of the secondary stream 11B.

The shutters 17 are in a retracted position in which they are housed in a cavity 19 of the movable cowl 16 so as not to block the secondary vein 11B.

Thus, in direct jet, the reverser 12 makes it possible to channel the secondary flow 10B towards the rear of the propulsion assembly 1 so that this secondary flow 10B fully contributes to the propulsion of the aircraft.

Figure 3 shows the reverser 12 in a reverse thrust configuration, also called a reverse jet. In this configuration, the movable cowl 16 is in an open position in which it releases a radial opening constituted in this example by openings of the grids 15. Indeed, the axial translation of the movable cowl 16, towards the rear of the propulsion unit 1 with respect to the front frame 14, uncovers the grids 15 which are integral with the front frame 14.

The sliding of the movable cowl 16 from the closed position (FIG. 2) to the open position (FIG. 3) causes the shutter flaps 17 to deploy in the secondary vein 11B. To do this, the shutter flaps 17 are hinged to the movable cowl 16 at an articulation point M1 and each of the rods 18 is connected at a first end S1 to a respective shutter flap 17 and at a second end S2 to the fixed internal structure 13.

In reverse jet, the shutters 17 are thus in a deployed position so as to deflect towards the grids 15 a part representing in this example substantially all of the secondary flow 10B (see FIG. 3).

In a manner known per se, the grids 15 comprise a blade making it possible to direct the secondary flow 10B passing through these grids 15 towards the front of the propulsion assembly 1.

In this thrust reversal configuration, the secondary flow 10B thus generates a braking counter-thrust of the aircraft.

To modify the configuration of the inverter 12, the latter comprises actuators such as cylinders (not shown) configured to move the movable cowl 16 between the closed position and the open position. These cylinders are in this example carried by the front frame 14 and are connected to the movable cowl 16 so as to exert thereon a pushing or pulling force, to move it respectively from upstream to downstream or from downstream to upstream.

By convention, moving the movable cowl 16 from the closed position to the open position defines a positive direction of movement D3 and its movement from the open position to the closed position defines a negative direction of movement.

In the embodiment of Figures 4 and 5, the guiding of the movable cowl 16 during its movement between the closed and open positions is achieved by cooperation of a first groove 21 with a sliding element 20 forming in this example a rail.

The rail 20 is integral with the movable cowl 16.

The first groove 21 is formed by a slide 22 secured to a retaining structure 23 which constitutes one of said fixed elements of the reverser 12.

In the open position, the movable cowl 16, cantilevered over the slide 22, is axially retained by the actuators.

In a conventional reverser, in particular in the event of breakage of an actuator and absence of emergency axial retention means, there is a risk of tilting of the movable cowl 16 under the action of the aerodynamic stresses to which it is subjected, and consequently a risk of dislocation of the movable cover 16 relative to the slide 22 (see Figure 6).

The inverter 12 of the invention comprises for this purpose braking elements 24 and 25 as described below with reference to Figures 7 to 10.

In the example of Figure 7, the first groove 21 of the slide 22 is delimited by a bottom face 26 and by two side faces 27 and 28 forming a U-shaped cavity. Of course, the first groove 21 can have any other shape making it possible to guide the movable cowl 16, for example a semi-circular shape.

The first groove 21 is configured to guide the rail 20 at least over a stroke C1 of the movable cowl 16 between the closed position and the open position.

Thus, when the movable cowl 16 is moved between the closed position and the open position, the rail 20 and the first groove 21 form first means for guiding the movable cowl 16.

The slide 22 comprises in this example a second groove 24, also U-shaped, opening onto the bottom face 26 of the first groove 21 (see FIG. 7).

In this example, this second groove 24 is configured to receive a pin 25 secured to the rail 20.

Referring to Figure 8 showing the pin 25 in a configuration in which the movable cover 16 is between the closed position and the open position, the second groove 24 and the pin 25 are respectively sized to allow frictionless sliding of the pin 25 in the second groove 24 over the entire stroke C1 of the movable cowl 16, that is to say when the latter is moved between the closed position and the open position (see direction D2 in Figure 8) . A slight friction of the pin 25 with the second groove 24 is however admissible, provided that this does not prevent the sliding of the movable cowl 16 between the closed position and the open position.

When the movable cowl 16 is moved in the positive direction beyond the open position, the pin 25 and the second groove 24 cooperate with each other by sliding with friction so as to generate a braking force s opposing this move.

More precisely, the second groove 24 and the pin 25 are configured so that the braking force increases when the movable cowl 16 moves away from the open position, in the positive direction of movement D3.

In this example, the second groove 24 has for this purpose a dimension E1 which varies according to the direction D2 of movement of the movable cowl 16.

Referring to Figure 8, the dimension E1 corresponds to a gap between two faces facing each other delimiting the second groove 24, this dimension E1 being considered perpendicular to the direction D2 of movement of the pin 25 when the movable cowl 16 is moved in the positive or negative direction.

On a first longitudinal portion of the slide 22, corresponding to the stroke C1 of the movable cowl 16 between the closed position and the open position, the dimension E1 of the second groove 24 is on the one hand constant along the direction D2 of movement of the pin 25 and, on the other hand, greater than the dimension E2 of the pin 25, the dimension E2 also being considered perpendicular to the direction D2 of movement of the pin 25 when the movable cowl 16 is moved in the direction positive or negative.

On a second longitudinal portion of the slide 22, corresponding to the travel C2 of the movable cowl 16 between the open position and a stop position (see below), also called overtravel, the dimension E1 gradually decreases so as to gradually increase the friction force between the pin 25 and the second groove 24 when the movable cowl 16 is moved in the positive direction between the open position and the stop position.

Figure 9 shows the pin 25 in a position in which the movable cowl 16 is in the open position.

Figure 10 shows the pin 25 in a position in which the movable cowl 16 is in the stop position.

In this example, the pin 25 has elastic properties allowing it to return to its initial shape, illustrated in figure 8, after undergoing a deformation as illustrated in figure 10.

In a non-limiting way, the pin 25 can have elastic, elasto-plastic or even elasto-visco-plastic properties.

Thus, when the movable cowl 16 is moved in the positive direction beyond the open position, the second groove 24 and the pin 25 are configured so that the braking force comprises at least one component perpendicular to the direction D2 of movement of the movable cowl 16 and of the pin 25.

The second groove 24 and the pin 25 form second means for guiding the mobile cowl 16. Indeed, the cooperation of the second groove 24 and the pin 25 simultaneously ensures the braking and the guiding of the mobile cowl 16.

In one embodiment, the movable cowl 16 is guided both by the first guide means 20 and 21 and by the second guide and braking means 24 and 25 when the movable cowl 16 performs the overtravel C2.

More generally, the first groove 21 can be configured to guide the rail 20 both over all or part of the stroke C1 and over all or part of the overtravel C2 of the movable cowl 16.

In the example of Figures 8 to 10, the slide 22 comprises a stop 29 configured to prevent the movement of the movable cowl 16 in said positive direction beyond the stop position, that is to say to block the movable cowl 16 when the latter reaches the stop position.

This stop 29 comprises a stop face 30 perpendicular to the direction D2 of movement of the pin 25 (see FIG. 8).

Such a stop 29 is optional since dimension E1 can be such that, at the end of overtravel C2, this dimension prevents as such any movement of pin 25 in the positive direction beyond the stop position. For example, dimension E1 can be zero at the stop position.

Figure 11 shows another type of stop 29 configured to plastically deform pin 25 when movable cowl 16 is moved to the stop position.

In an embodiment not shown, the braking elements are structurally separated from the guide means of the movable cowl 16. For example, said second groove 24 can be made in a separate part from the slideway 22.

More generally, what has just been described is in no way limited to braking elements comprising one or more grooves 24 and one or more pins 25. The braking force can result from the cooperation of any other type of elements braking, or the cooperation of any other type of guiding and guided elements.

The mobile external structure 16 can also be a pivoting structure such as a door of a door inverter.

Claims (10)

Thrust reverser (12) for an aircraft propulsion system (1), this reverser (12) comprising a fixed structure and a mobile external structure (16), this reverser (12) being configured to be placed in:
– a direct jet configuration in which the mobile external structure (16) is in a closed position, the mobile external structure (16) in the closed position being capable of guiding a flow of fluid (10B) in the propulsion assembly ( 1) so as to generate thrust,
– an inverted jet configuration in which the mobile external structure (16) is in an open position, the mobile external structure (16) in the open position giving off a radial opening capable of evacuating a part of said fluid flow (10B ) of the propulsion assembly (1) so as to generate counter-thrust,
the movement of the movable external structure (16) from the closed position to the open position defining a positive direction of movement (D3), this reverser (12) being characterized in that the fixed structure comprises a first braking element (24) and the mobile external structure (16) comprises a second braking element (25), the first (24) and the second braking element (25) cooperating with each other by sliding with friction when the structure mobile outer (16) is moved in the positive direction (D3) beyond the open position so as to generate a braking force opposing this movement, the first (24) and the second braking element ( 25) being configured so that the braking force increases when the mobile outer structure (16) moves away from the open position. Reverser (12) according to Claim 1, in which the first (24) and the second braking element (25) are configured so that the braking force comprises at least a component perpendicular to a direction (D2) of displacement of the mobile external structure (16). Reverser (12) according to claim 1 or 2, wherein one of the first (24) and the second braking element (25) comprises at least one guide element (24) such as a slider and the other among the first (24) and the second braking element (25) comprises at least one guided element (25) such as a pin, said braking force resulting from the cooperation between the guiding element (24) and the guided element (25). Inverter (12) according to Claim 3, in which the at least one guide element (24) forms a groove configured to receive the at least one guided element (25), this groove (24) having a dimension (E1) which varies along a direction (D2) of displacement of the mobile external structure (16). Reverser (12) according to any one of Claims 1 to 4, this reverser (12) comprising first guide means (20, 21) configured to guide the mobile external structure (16) between the closed position and the closed position. opening and second guide means (24, 25) configured to guide the mobile external structure (16) when the latter is moved in the positive direction (D3) from the open position, these second guide means (24 , 25) comprising the first and second braking elements. Reverser (12) according to any one of Claims 1 to 5, this reverser (12) comprising a slideway (22) integral with one of the fixed structure and the mobile external structure (16) and a sliding element (20) secured to the other among the fixed structure and the mobile external structure (16), this slide (22) forming a first groove (21) configured to receive the said sliding element (20), the slide (22) forming a second groove ( 24) forming one of the first (24) and the second braking element (25), the second groove (24) being configured to receive the other of the first (24) and the second braking element (25) . Reverser (12) according to any one of Claims 1 to 6, this reverser (12) comprising a stop (29) configured to prevent the displacement of the movable external structure (16) in the said positive direction (D3) beyond a stop position, the abutment (29) being configured so that the mobile external structure (16) is subjected to said braking force when the latter is moved in the positive direction (D3) between the open position and the stop position. Reverser (12) according to Claim 7, in which one of the first (24) and the second braking element (25) is configured to cooperate with the stopper (29) when the mobile external structure (16) is moved until 'in the stop position so as to immobilize the mobile external structure (16) in the stop position. Reverser (12) according to Claim 8, in which one of the abutment (29) and the braking element (25) cooperating with this abutment (29) is configured to be plastically deformed by the other of the abutment ( 29) and the braking element (25) cooperating with this stop (29) when the mobile external structure (16) is moved to the stop position. Aircraft propulsion assembly (1), this propulsion assembly (1) comprising a thrust reverser (12) according to any one of the preceding claims.